Answer:
C. $12,400
Explanation:
$1116 of Charlie's paycheck represented 9% of his sales, so his sales were ...
... $1116/0.09 = $12,400
_____
In generic terms, when you have ...
value = fraction × (whole amount)
you can divide by the fraction to find the whole amount:
value/fraction = (whole amount)
Here, the value is the portion of Charlie's pay that is due to the commission, and the fraction is the commission rate. The whole amount is the quantity of sales we're trying to find.